Lubricating compositions



' certain United States Patent 2,713,558 LUBRICATING COMPOSITIONS Howard E. Schmitz, Alton, Ill., assignor to Shell Development Company, New York, N. Y., a corporation of Delaware No Drawing. Application May 24, 1954,

Serial No. 432,027

9 Claims. (Cl. 25233.6)

This invention relates to lubricants, and more particularly to mineral lubricating oil compositions which are suitable for lubrication under extreme operating conditions such as under extreme pressure and wear conditions.

It is well known that the high pressure occurring in types of gears and bearings may cause a film of lubricant to rupture with consequent damage to the machinery. It has been shown that base lubricants, such as mineral oil and/or synthetic oil, can be improved, with regard to their protective effect on rubbing surfaces, by the addition of certain substances, so that excessive wear, scufling and seizure, which normally follow a break in the film of lubricant, can thus be prevented even under the most unfavorable pressure and speed conditions. Oils possessing this highly desirable property are called extreme pressure lubricants.

It is known that certain elements or compounds of elements of the type of chlorine and phosphorus are capable of imparting extreme pressure properties to lubricants, which may be lubricating oils and greases, when blended therewith. Among the compounds heretofore used are phosphoric acid esters, free or loosely bound sulfur, and certain chlorinated organic compounds.

It has now been discovered that improved extreme pressure lubricants are obtained by incorporating into a base lubricant a minor amount of an oil-soluble selenium N- organo-substituted thiocarbamate, which may be either the divalent or tetravalent selenium thiocarbamate (including both monoand di-thiocarbamates). The N- organo substituent(s) is an oleophilic organic radical and usually is a hydrocarbon radical, generally attached to the N-atom by an acyclic or alicyclic C-atom (or two such C- atoms in the case of heterocyclic N-containing structures and 'thiocarbamates from secondary amines). The divalent selenium thiocarbamates are preferred for the purpose of the invention. Still further, it has been found that mixtures of the selenium salts and a thiuram polysulfide are particularly efiective in providing extreme pressure properties in lubricating oil compositions thereof. As a still further aspect of the invention, it has been found that the selenium carbamates are particularly effective in providing lubricating oils with outstanding extreme pressure properties when used together with metal salts, such as lead naphthenate, either with or without the thiuram polysulfide.

Thus, whereas, in a comparative evaluation ina standardized test, lead naphthenate, known to be an extreme pressure agent, reached a scar diameter of 2 mm. at only 200 kilograms load and welded at 300 kg., divalent selenium dibutyldithiocarbamate gave a scar of about 2 mm. only after a load of 400 kg. was applied and welding did not occur until a load of 600 kg. was applied.

The selenium thiocarbamates are represented by the general formula:

(RR1NCX1X2)21IS6 wherein n is a whole number from 1 to 2, R is a hydro- 2,7 13,558 Patented July 19, 1955 carbon radical, such as alkyl, aralkyl, cycloalkyl or heterocyclic radicals, and R1 is hydrogen or the same as R, X1 and X2 are selected independently from oxygen and sulfur, at least one of them being sulfur. The pre- Thethiuram polysulfides which are useful in combination with the selenium salts of this invention can be represented by the general formula:

wherein R and R1 have the same designations as specified in connection with the selenium thiocarbamates and preferably correspond to the Rs of the thiocarbamate and n is at least 2, usually from 2 to 4.

Thiuram sulfides can be prepared by any suitable means, such as described in U. S. Patents 2,251,686, 2,286,690, 2,423,310, 2,464,799, and 2,647,145.

As already stated, the N-atom should be attached directly to an acyclic or alicyclic C-atom of the substituent radlcal. This C-atom may be either primary,

ethyl, dipyridyl, dimorpholine amines.

The following examples illustrate methods of preparng the divalent selenium carbamate compounds for use in compositions of this invention.

molar portion of selenium dioxide dissolved stantial rise in temperature. The resulting product, after removal of the alcohol by vaporization, is an equimolar mixture of divalent selenium dibutyldithiocarbamate and tetrabutyl thiuram disulfide. If desired, the tetrabutyl thiuram disulfide can be separated from the mixture and the selenium salt used as the oil additive in compositions of this invention. However, it is preferred to use the mixture as the oil additive without recourse to separation.

Other specific divalent selenium salts together with their corresponding thiuram disulfides which can be used in compositions of this invention include divalent and tetravalent (divalent preferred) selenium dimethyl monoand dithiocarbamates; diethyl monoand diethiocarbamates, diamyl monoand dithiocarbarnates; dihexyl monoand dithiocarbamates; dioctyl monoand dithiocarbamates; N-ethyl-N-phenyl monoand dithiocarbamates; dicyclohexyl monoand dithiocarbamates; monocetyl monoand dithiocarbamates; di(cetylphenyl) monoand dithiocarbamates; dibenzyl monoand dithiocarbamates', diamyl-piperidyl monoand dithiocarbamates; dibutyl carbamate; dihexyl carbamate; dicyclohexylcarbamate; and monocetylcarbamate.

The oil-soluble selenium salts with or without the corresponding thiuram polysulfides can each be used in amounts ranging from 0.01% to 10% and preferably from 0.1% to about 5% by weight in various types of lubricating oils such as natural and synthetic hydrocarbon oils, synthetic polar containing lubricants such as esters of polycarboxylic acids, polyalkylene oxide polymers, silicon polymers and mixtures thereof, said oils ranging in viscosity from 50 SUS at 100 F. to above 200 SUS at 210 F.

A particularly preferred embodiment of this invention is provided by combining the above type of additives with an oil-soluble metal salt of a cyclic carboxylic acid such as the polyvalent metal salts of naphthenic acid, abietic acid, rosin acid of which preferred are the lead, tin, aluminum and zinc salts of naphthenic and abietic acids.

The naphthenic acids and their refined product can be prepared by the processes described in U. S. Patents 2,200,711, 2,214,438, 2,296,039, and 2,537,576. The molecular weight of the naphthenic acid can vary from 200 to above 1000 and preferably from 350 to 600.

The salts as described above such as lead naphthenate and the others can be used in amounts ranging from 0.01% to 10% and preferably from 0.1% to about 5% by weight.

The general formulation of compositions of this invention can be represented by:

Amount, percent wt.

Broad Preferred Range Range Primary additives Se salts of thiocarbamic acids 0. 01-10 0. 1-5

Secondary additives Thiuram sulfide 0. 01-10 0.1-5

Optional additives Salts of carboxylic acids and/0r organic compounds containing inorganic acid radicals, e. g. lead naphthenates, sultonates, etc 0-10 0. 1-5

Base

Natural oil, e. g., mineral oil, fuel oil, synthetic oil, fixed oils and mixtures thereof Balance Balance The following examples are suitable compositions for the practice of this invention in which the selenium is divalent unless otherwise indicated.

Example 1: Percent by Wt.

Se dibutyldithiocarbamate 6.6

4 Example 1-Continued Percent by weight Pb petroleum naphthenate (MW 450) 6.7 Mineral lubricating oil (SAE 30) Balance Example 2:

Se dibutyldithiocarbamate 5 Pb petroleum naphthenate 5 Di(2-ethylhexyl)sebacate Balance Example 3:

Se dibutyldithiocarbamate 1.5 Tetrabutylthiuram disulfide l 5 Pb petroleum naphthenate 3 Mineral lubricating oil (SAE 30) Balance Example 4:

Se dibutylmonothiocarbamate 3.5 Pb petroleum naphthenate 5 Phenyl-a-naphthylamine 0.1 Mineral lubricating oil Balance Example 5:

Se dihexyldithiocarbamate 1 pb petroleum naphthenate 2 Mineral lubricating oil Balance Example 6:

Se dibenzylthiocarbamate 1.2 Pb petroleum sulfonate 2.5 2,6-ditert-butyl-4-methylphenol 0.1 Mineral lubricating oil Balance Example 7:

Se dicyclohexyldithiocarbamate 1.8 A1 petroleum naphthenate 1 Mineral lubricating oil Balance Example 8:

Se monobutyldithiocarbamate 1 Zn petroleum naphthenate 1.5 Mineral lubricating oil Balance Example 9:

Se dibutylmonothiocarbamate 0.25 Pb abietate l Tetrabutylthiuram disulfide 0.25 Mineral lubricating oil Balance Example 10:

Tetravalent Se dibenzyldithiocarbamate 0.5 Pb petroleum sulfonate 1.5 Mineral lubricating oil Balance Example 11:

Se dibenzylmonothiocarbamate 2.5 Pb abietate 1.8 Mineral lubricating oil Balance Example 12:

Se diethylmonothiocarbamate 0.75 Tetraethylthiuram disulfide 0.75 Pb petroleum naphthenate 3 Mineral lubricating oil (SAE 30) Balance Example 13:

Se dibutyldithiocarbamate 0.5 Pb petroleum naphthenate 0.5 Fuel oil Balance Example 14:

Se diethylmonothiocarbamate 0.75 Tetraethylthiuram disulfide 0.75 Al petroleum naphthenate 3 Mineral lubricating oil (SAE 30) Balance Example 15: Tetravalent Se dicyclohexyldithiocarbamate 0.5 Pb petroleum sulfonate 1.5 Di(2-ethylhexyl)sebacate Balance Example 16:

Se dihexyldithiocarbamate 0.5 Pb petroleum naphthenate 0.25 Pb petroleum sulfonate 0.25 Mineral lubricating oil Balance Example 17:

Se dibutyldithiocarbamate 0.5 Tricresylphosphate 0.25 Pb petroleum naphthenate 0.25 Mineral lubricating oil V Balance Example 18: Percent by weight The synergistic effects produced by the additive blend Se dibutyldithioparbamate of this invention are clearly shown by the following Mineral lubricating oil Balance additional data, also obtained on the four-ball EP Example l9: tester. The flash temperature parameter is the maxi- Se dibutyldithiocarbamate 3.3 mum value reached by the ratio P/d Where P is T trabutylthruram disulfide 3.3 the applied load in kilograms and d is the scar diameter Mineral lubncatmg o1l, Balance in millimeters at the end of second runningg RR Percent w. Mean Pe1-eentw.SeleniumDibuty1 Tetrabutyl Percent Flash Hertz Base Oil dN h- Dithm-Carbamate 5 2 ggg g Lad,

o 0 3-.-- 0 0 0 0 0 0 3 Do .1 5i 0' For Comparison:

Mineral Oil 3% Zine Dibutyl Dithiocarbamate. Do 3% PrSs-terpene Reaction Product.

Example Percent by weight Compositions of this invention can be modified by Se dibutyldithiocarbamate 1.5 addition thereto of minor amounts (0.01-1%) of anti- Mineral lubricating oil Balance OXidantS, corrosion inhibitors, extreme pressure agents,

Example 21: antiwear agents and the like such as alkyl phenols Se dibutyldithiocarbamate 3 (2,6-ditertbutyl-4-methylphenol), amines, e. g., phenyl- Pb petroleum naphthenate 1 naphthylamine; organic phosphorus compounds, e. g., Mineral lubricating oil Balance ilorol phosphate, dilauryl phosphite, tributyl phosphate,

Example 22: I tricresyl phosphate; sodium nitrite, lithium nitrite, etc.

Se dibutyldithiocarbamate 3 This application is a continuation-in-part of our ap- Pb petroleum naphthenate 2 pl tion, Serial No. 215,185, filed March 12, 1951, now Mineral lubricating oil Balance abandoned.

Example 23: I claim as my invention:

Se dibutyldithiocarbamate 3.3 1. A l bricating composition comprising a major Tetrabutylthiuram disulfide 3.3 amount of a mineral lubricating oil and from about Pb petroleum naphthenate 6.7 0.1% to about 10% of an oil soluble divalent selenium Mineral lubricating oil Balance dihydrocarbyl dithiocarbamate.

Example 24; 2. A lubricating composition comprising a major Se dibutyldithiocarbamate' 5 amount of a mineral lubricating oil and from about Pb petroleum naphthenate 5 .1% to about 5% each of an oil-soluble divalent Mineral lubricating oil Balance selenium dihydrocarbyl dithiocarbamate and a thiuram Compositions of this invention were evaluated for their extreme pressure properties by use of the four-ball extreme pressure lubricant tester neering, vol. 136, July 13, 1953. prises four steel balls arranged in a pyramid formation. The top ball is held in a chuck and rotated against the three bottom balls which are clamped in a stationary ball holder. The balls were immersed in the composisition to be tested. Tests were run under conditions indicated in the following table outstanding extreme pressure as described in Engi- This apparatus comcompounds.

polysulfide.

3. A lubricating composition comprising a major amount of a mineral lubricating oil and from about 0.1% to about 5% each of an oil-soluble divalent selenium dihydrocarbyl dithiocarbamate, a thiuram polysulfide and up to 10% of a metal salt of an organic cyclic acid.

4. A lubricating composition comprising a major amount of a mineral lubricating oil and from about 0.1% to about 5% each of an oil-soluble divalent selenium and compared with other dialkyldithiocarbamate and a polyalkyl thiuram disulfide.

5. A lubricating composition comprising a major Four-ball evaluation of E. P. compositions [Fixed conditions: One minute, 1500 R. P. M. at ambient temperature, steel on steel. Base lubricant: Refined mineral oil] Amount Sear Diameter (mm.) at Various Loads (Kg.) Additive (Percent) 400 I 500 I 600 I 700 Selium dibutyl-dithiocarbamate 6. 6

Lead naphthenate (Example 1) 6. 7

Selenium dihutyl-dithiocarbamate 3. 3

Tetrabutylthiuram disulflde. 3. 3

Lead naphthenate (Example 23) 6. 7

36181113111111 dibutyl dithioearbamate. 0

Tetrabutylthiuram disulfide (Example 19) 3. 3

Dodeeyl diselenide 4. 4 Tributyl se] 1 Lead N aph 0 P205 treated eastor oil..

W means welding of the tour balls has occurred.

amount of a mineral lubricating oil and from about 0.1% to about 5% each of an oil-soluble divalent selenium dialkyldithiocarbamate, a polyalkyl thiuram disulfide and up to 10% of an oil-soluble metal naphthenate.

6. A lubricating composition comprising a major amount of a mineral lubricating oil and from about 0.1% to about 5% each of an oil-soluble divalent selenium dibutyldithiocarbamate and tetrabutyl thiuram disulfide.

7. A lubricating composition comprising a major amount of a mineral lubricating oil and from about 0.1% to about 5% each of an oil-soluble divalent selenium divalent dibutyldithiocarbamate, tetrabutyl thiuram disultide, and up to 10% of an oil-soluble lead naphthenate.

8. A lubricating composition comprising a major amount of mineral lubricating oil, from about 3% to about 6.6% of a divalent selenium dibutyl dithiocarbamate, up to about 3.3% of tetrabutyl thiuram disulfide and up to about 6.7% of lead naphthenate.

8 9. A- lubricating composition comprising a major amount ot mineral lubricating-oil, from about 0.1% to about 6.6% of divalent selenium dibutyl dithiocarbamate from about 0.1% to about 3.3% of tetrabutyl thiuram disulfide and from about 0.1% to about 6.7% of lead naphthenate.

References Cited in the file of this patent UNITED STATES PATENTS 1,622,534 Murrill Mar. 29, 1927 2,211,798' Story Aug. 20, 1940 2,347,128 Russell Apr. 18, 1944 2,367,355. Kaufman Jan. 16, 1945 2,450,633 Clayton Oct. 5, 1948 

1. A LUBRICATING COMPOSITION COMPRISING A MAJOR AMOUNT OF A MINERAL LUBRICATING OIL AND FROM ABOUT 0.1% TO ABOUT 10% OF AN OIL SOLUBLE DIVALENT SELENIUM DIHYDROCARBYL DITHIOCARBAMATE. 